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Jan 1, 2010 (Vol. 30, No. 1)

Making Strides in the Biodetection Arena

New Types of Arrays, Novel Combinations of Capabilities, and Increased Speeds Revitalize Field

  • A new approach to high-throughput screening has been developed by microPEP. Rather than imprint reagents onto microarrays, microPEP’s approach injection-molds microwell arrays to be used with microbeads. These microarrays contain 40 million locations that are 3 µm in diameter and 3 µm deep, making them the smallest microwell arrays in the world, according to the company.

    “This molded slide is meant to be an option to the 25 x 75 mm microarrays,” according to Scot MacGillivray, business development manager. “We think we’re the only company in the world to offer this,” MacGillivray reported at the Knowledge Foundation conference on “Detection Technologies” late last year.

    “This molded microarray has the potential to change the way healthcare is delivered and assays are performed,” and it certainly makes high-throughput screening more cost effective. For example, traditionally microbead assays could only be performed by first etching away a silicon wafer. That’s expensive, costing hundreds of dollars. Molding that substrate, however, costs less than $30, MacGillivray says. “When we get into the area of thousands of slides, the cost is under $10 per microwell slide.” The microwell slides meet Class 10,000 cleanroom specifications.

    The tooling is based upon standard injection technology and some proprietary technology. The next step for microPEP is to explore the submicron fabrication limits. “We’re interested in trying nanofeatures,” MacGillivray said. Additionally, the company has developed 50 and 100 µm well slides. The 3 µm microwell slides are available now.

    While microPEP is advancing miniaturization for biodetection, other presenters discussed new types of arrays, expanded capabilities, increased speeds, new combinations of capabilities, and novel molecular methods to immobilize and label DNA.

  • Liquid-Crystal Assays

    Click Image To Enlarge +
    Platypus Technologies is developing protein-detection assays based on liquid-crystal technology.

    Platypus Technologies is developing protein-detection assays based upon liquid-crystal technology to rapidly detect and report the presence of target molecules bound to specially designed surfaces. 

    As Richard Schifreen, Ph.D., president and CEO, explained, liquid-crystal molecules are rod-shaped and tend to align parallel with each other. That alignment changes, however, when target molecules bind to receptors that are immobilized on the surface of liquid crystal-coated substrate. The standard analogy compares the alignment to upright bowling pins, and the binding to the scattered pins after the bowling ball—the target molecule—has struck.

    The dramatic difference makes direct detection of viruses captured by surface-bound antibodies possible with low- or no-power readouts based upon interrogation with polarized light. For a simple “yes/no” readout, a light image indicates presence of the target molecule and a dark image indicates absence of the target.

    “The work is at the precommercialization phase,” Dr. Schifreen said. “The sensor can be packaged into an instrument, a badge, a handheld device, or incorporated into an alarm system.”

    Platypus is currently developing a protein-detection assay for influenza exposure and water-borne pathogens, and gas sensors to detect nitric oxide and pesticides and to monitor asthma. “The advantages,” he said, “are low- or no-energy requirements, the inherent flexibility of a single format for multiple analytes, and the simplicity of a solid-state system. It’s very inexpensive, costing a couple of dollars at research scale,” versus about $100 for an electrochemical sensor.

    “Detection speed depends on the particular system,” Dr. Schifreen said, but ranges from a few seconds to one or two minutes. “The assay can be either qualitative or quantitative. We’re working to optimize the system so it’s more specific, more reproducible, and, in some applications, reversible.”

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